• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2261-2266
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• 2009

A novel adaptive phase calibration method is proposed for nonlinear amplifiers. Based on the adaptive process of simple phase vector calculations, the AM/PM distortion can be significantly reduced for various input power. The performance of the proposed method is evaluated for up to 80 % improvements in AM/PM distortions, compared with the distortion of a conventional amplifier. Moreover, by means of an additional envelope-compensation technique, the improvement of the adjacent channel power ratio (ACPR) is presented.

• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.319-324
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• 2018

In this paper, a high power amplifier using RF power solid-state semiconductor is implemented to overcome a problem of plasma generator which has the low efficiency, short life span, the difficult maintenance and the high-operation cost. This power amplifier consists of a radial combiner of low-loss and high power operation and the sixteen 300 W power amplifiers to obtain 3 kW output power for high power operation implemented in semiconductors at industrial scientific medical (ISM) band of 2.45 GHz. In addition, this amplifier overcomes the problem of heat generation due to high power by applying a water-cooled structure to the individual amplifiers. This power amplifier, which is made up of a small system, achieves 50% efficiency at the desired output.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.231-238
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• 2019

In this paper, we have studied how to improve the amplifiers efficiency by minimizing the combining loss when several unit power amplifiers are combined to obtain high output power. Specifically, we have developed Ka-band Spatial Combining Amplifier. The fabricated Spatial Combining Amplifier is a Ka-band 20W class SSPA, which uses a 5W class unit amplifier module 8EA designed using a GaN bare die. We also combined The unit amplifier module using 8-way spatial divider and combiner with a hybrid radial structure. The output combining loss of the fabricated spatial coupler is about 0.334dB, which is about 92.6% efficiency. In this paper, we developed a Spatial Combining Amplifier with a maximum saturation output of 10W and a power addition efficiency of over 15%. As a result, we achieved the maximum saturation output of 30W and the power addition efficiency of 19%.

• The Journal of the Acoustical Society of Korea
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• v.25 no.6
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• pp.282-290
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• 2006

This paper proposes a new Digital Reverberator that models Analog Helical Coil Spring Reverberator for guitar amplifiers. While the conventional digital reverberators are proposed to provide better sound field mainly based on room acoustics, no algorithm or analysis of digital reverberators those model Helical Coil Spring Reverberator was proposed. Considering the fact that approximately $70{\sim}80$ percent of guitar amplifiers are still with Helical Coil Spring Reverberator, research was performed based not on Room Acoustics but on Helical Coil Spring Reverberator itself as an effector. After performing simulations with proposed algorithm, it was confirmed that the Digital Reverberator by proposed algorithm provides perceptually equivalent response to the conventional Analog Helical Coil Spring Reverberators.

• The Journal of the Acoustical Society of Korea
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• v.25 no.6
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• pp.291-297
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• 2006

This paper proposes a new Digital Reverberator that models Analog Helical Coil Spring Reverberator for guitar amplifiers. While the conventional digital reverberators are proposed to provide better sound field mainly based on room acoustics, no algorithm or analysis of digital reverberators those model Helical Coil Spring Reverberator was proposed. Considering the fact that approximately $70{\sim}80$ percent of guitar amplifiers are still with Helical Coil Spring Reverberator, research was performed based not on Room Acoustics but on Helical Coil Spring Reverberator itself as an effector. After performing simulations with proposed algorithm, it was confirmed that the Digital Reverberator by proposed algorithm provides perceptually equivalent response to the conventional Analog Helical Coil Spring Reverberators.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.443-450
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• 2000

Although designing a virtual topology for all-optical WDM wide-area networks has been extensively studied and several algorithms have been proposed, these algorithms assumed error-free communication between two nodes. However, noises from optical amplifiers and optical cross-connects can degraded the signal, resulting in a nonzero bit-error rate. In this paper, we investigate the effect of physical limitations on the virtual topology design. We show that for side-area all-optical networks where transmission distance is fairly long, virtual topology design algorithm that can determine the locations of opto-electronic(OE) and electro-optic(EO) conversions to set up a connection request with a high BER in a multihop manner.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.99-106
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• 2001

An overview of Silicon Carbide (SiC) Static Induction Transistor (SIT) development is presented. Basic conduction mechanisms are introduced and discussed, including ohmic, exponential, and space charge limited conduction (SCLC) mechanisms. Additionally, the impact of velocity saturation and temperature effects on SCLC are reviewed. The small-signal model, breakdown voltage, power density, and different gate structures are also discussed, before a final review of published SiC SIT results. Published S-band (3-4 GHz) results include 9.5 dB of gain and output power of 120 W, and L-band (1.3 GHz) results include 400 W output power, 7.7 dB of gain, and power density of 16.7 W/cm.

• ETRI Journal
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• v.27 no.5
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• pp.563-568
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• 2005

A motion-control chip contains major functions that are necessary to control the position of each motor, such as generating velocity command profiles, reading motor positions, producing control signals, driving several types of servo amplifiers, and interfacing host processors. Existing motion-control chips can only generate velocity profiles of fixed characteristics, typically linear and s-shape smooth symmetric curves. But velocity profiles of these two characteristics are not optimal for all tasks in industrial robots and automation systems. Velocity profiles of other characteristics are preferred for some tasks. This paper proposes a motion-control chip to generate velocity profiles of desired acceleration and deceleration characteristics. The proposed motion-control chip is implemented with a field-programmable gate array by using the Very High-Speed Integrated Circuit Hardware Description Language and Handel-C. Experiments using velocity profiles of four different characteristics will be performed.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.2
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• pp.22-27
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• 1978

An improved active R filter is proposed which contains only resistors and two operational amplifiers represented by their single pole model. The filter has very low sensitivities to all circuit parameters, is suitable for low frequency and low 9 applications in addition to high frequency and high 0, and realizes various biquadratic transfer functions simultaneously with lower resistance ratios. The independent control of design specifications is possible in the circuit. Experimental results in laboratory are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.6 no.1
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• pp.51-57
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• 1981

Carriers moving in a semiconductor can impart gain or loss to an acousic wave traveling through Piezo-electric materials. In this paper, surface a coustic wave amplifiers, which employ the interaction between carriers drifting in a semiconduct or film and electic fields accompanying a Rayleigh wave propagating on a Piezoelectric substrate, are described. The effect of various electromagnetic boundary condition on th propagation of surface waves in Piezoelectrics is considered. An expression for the dependence of surface wave velocity on electic boundary conditions is derived. Calculations show that, for properly prepared material, significant amplification is expected up to the microwave frequencies. At high frequencies, gain is reduced because electro diffusion smooths out the electron bucning necessary for amplification.